One system for monitoring a sensor is provided in U.S. Pat. No. 7,526,914. This system presents a controller configured to calculate heat data corresponding to a heat budget in the exhaust pipe in close proximity to a sensor after an engine startup. The heat estimate is based upon an operating condition of the engine and a driving condition of a vehicle. The controller also makes a determination as to dryness inside the exhaust pipe based upon the heat data. Further, the power supply to the sensor heater is controlled based upon the result of the dryness determination.
The above-mentioned method can also have several disadvantages. Specifically, the system uses exhaust gas oxygen concentration and other variables to estimate when conditions in the vehicle exhaust system are dry enough to start heating an oxygen sensor. Since the sensor heater activation is related to an estimate of exhaust system conditions rather than to actual exhaust system conditions, the sensor heater may be activated earlier or later than is desired. As a result, the sensor may degrade at an undesirable rate if the heater is activated earlier than desired. On the other hand, if the sensor heater is activated later than desired, engine emissions may degrade.
The inventors herein have recognized the above-mentioned disadvantages and have developed a system for improving operation of an engine having a particulate matter sensor.
One embodiment of the present description includes a system for activating an exhaust sensor, comprising: an engine; an exhaust gas sensor; a particulate matter sensor; and a controller that activates a heater of said exhaust gas sensor when an output of said particulate matter sensor exceeds a threshold value after said engine is started.
By monitoring the output of a particulate matter sensor, the control of heater elements of other sensors located in the exhaust stream of an engine may be improved. For example, during an engine cold start, water condensate may form in the exhaust system as exhaust gases flow through the exhaust system. If a heating element of an oxygen sensor is activated before the water condensate leaves the exhaust system, performance of the oxygen sensor may degrade. On the other hand, if the oxygen sensor heater is activated later than desired, engine emissions may degrade. The inventors herein have developed a system where sensor heaters may be activated in relation to the output of a particulate matter sensor.
Specifically, in one example, when the output of the particulate matter sensor provides a near impulse output, sensor heaters may be activated. The near impulse response of the particulate matter sensor results from a rapid change in the conductivity of the particulate matter sensor in the presence of water condensate. In one embodiment, when the particulate matter sensor response is below a second threshold, after exceeding a first threshold, the particulate matter sensor is indicating that water condensate is no longer present in the exhaust system; therefore, sensor heaters can be activated. In this way, the inventors herein have developed a way to activate exhaust system sensor heaters in response to exhaust system conditions rather than by inferences that may be less reliable.
The present description may provide several advantages. Specifically, the approach may improve engine emissions by allowing sensor heaters to bring sensors up to operating temperatures earlier and more reliably than systems that infer exhaust system conditions. Further, the system can reduce sensor degradation by reducing the possibility of activating sensor heaters before water in the exhaust system is vaporized.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.